Maximum Yield Modern Growing | Vol. 21 Issue 01 2019

One of the main advantages of NFT, apart from the cost and labor savings of not
requiring large volumes of a growing substrate, is it allows production of salad greens,
lettuce, and herbs without the risk of grit contamination which can occur in soilless
substrate systems. NFT systems may incorporate heating or cooling of the nutrient solution
as is required for year-round cropping and allow a very ‘clean’ system to be run,
with sterilization of equipment between crops if necessary.
The main disadvantage of NFT is that power outages, which halt the continual flow of
nutrient, can quickly result in crop death, particularly under warm growing conditions.
Top: Multi-level NFT systems maximize
growing space.
Bottom: Vertical systems are ideal for
lightweight NFT channels.
“NFT systems may seem more complex
than substrate-based types of hydroponics,
however, they are extremely flexible with
regards to size, design, and equipment.”
FLEXIBILITY OF NFT SYSTEMS
NFT systems may seem more complex than substrate-based types of hydroponics,
however, they are extremely flexible with regards to size, design, and equipment.
A small basic system can comprise a single growing channel for production of a
few plants, a plastic bucket or bin for a nutrient reservoir, and a small aquarium
pump to circulate the nutrient solution. NFT growing
channels with a flat base profile can be purchased, however,
over the decades many innovative materials have been
used where these are not available. These include rainwater
down pipes, large diameter bamboo, channels formed from
timber, metal, or concrete and lined with plastic and long
rolls of plastic film itself folded into channels. These types of
basic NFT systems require manual checking and adjustment
of the electrical conductivity (EC) and pH of the nutrient
solution, and regular water level adjustments.
Commercial NFT systems are typically far more automated
than hobby systems and make use of electronic and
computer-controlled EC, pH adjustment, and float valves to
replace water used in the system. Advanced commercial
NFT systems may also utilize dissolved oxygen and solution
temperature measurements to monitor these root zone
variables. An NFT-based growing operation often has both
seedling and finishing NFT benches through which the plants
progress during production. Seedling systems have plants at
a much higher density, which are moved to a wider spacing
in the finishing system to maximize the growing area inside
greenhouses. Other NFT systems include moveable channel
systems where the distance between adjacent channels is
increased as the plants grow. Vertical NFT systems are also
popular and optimize growing space for lower-light crops
such as lettuce and some herbs. NFT systems can also be
installed outdoors or under basic shade covers.
IMPORTANT NFT FACTORS TO CONSIDER
Constructing and running a successful NFT system is reliant
on a few vital factors. These include slope, flow rate, nutrient
reservoir size, channel volume, and pump capacity. For those
purchasing an NFT system kitset, choose a reliable supplier with
a good reputation and these variables will already have been
factored into the design. For home-built systems, some consideration
needs to be given to all components and equipment. The
channels must be positioned on a slope so the nutrient solution flows steadily down at
a good flow rate, which for most systems is around 0.26 gallons/minute. Some systems
allow the channel slope to be adjusted and increased as the root system develops and
expands inside the channels, ensuring nutrient ponding does not occur. The dimensions
of the NFT channels are dependant on the type of plants being grown. Small
lettuce and herbs may be grown in standard NFT channels of four inches wide and two
inches high made from UV stabilized FDA approved high density polyethylene. Larger
plants like cucumbers and tomatoes require a wider and taller channel to accommodate
their considerably larger root system.
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Maximum Yield